Acetals and ketals are readily obtained by the reaction of aldehyde or ketone hydrocarbons and polyhydroxy hydrocarbons by many methods well known in the art. There are many references to the efficient preparation of these materials. It is desirable to prepare 2-alkoxy-ethanol compounds, such as 2-n-butoxyethanol and 2-n-propoxyethanol without the requirement of using ethylene oxide as the reactant. It is also desirable to have a process which is robust enough to prepare other hydroxy ether compounds without the requirement of using other highly reactive epoxy compounds and similar materials such as propylene oxide, 1,2-epoxybutane, glycidol (2,3-epoxy-1-propanol) and trimethylene oxide. It is also desirable to prepare hydroxy ether compounds in high selectivity without requiring alkylating agents such as alkyl bromides, chlorides and sulfates in their reaction with polyhydroxy compounds in a Williamson ether synthesis with the concurrent production of waste salts.
The classes of compounds known as hydroxy ether hydrocarbons have great value as solvents and dispersants for latex paints and other coatings. They also have value as components of industrial and consumer cleaning solutions and surfactants and raw materials for the preparation of polyurethane materials. The large bulk of this class of compounds that are commercially available are generally known as “E-series” and “P-series” solvents. The “E-series” solvents are prepared by the reaction of ethylene oxide (EO) with corresponding alcohols to form the “E-series” products. Conversely, the “P-series” of solvents are prepared by the reaction of propylene oxide (PO) with corresponding alcohols to form similar materials. This technology has a number of concerns and difficulties. First, ethylene oxide and propylene oxide are hazardous materials. Likewise, the nature of the reaction of an alcohol with highly reactive epoxides generates relatively low selectivity for desirable mono addition of EO or PO to the alcohol resulting in di-, tri and poly-EO or PO addition products in significant amounts. Third, the technology of mono ethylene glycol (MEG) production is moving away from the traditional isolation of ethylene oxide and subsequent reaction with water toward more efficient methods to prepare MEG in higher yield that use other technology, such as ethylene carbonate and direct water quenching of crude EO reactor product. These newer technologies remove a ready source of on-site EO for the production of E-series products. Fourthly, historically, a large capital intensive EO/MEG facility needs to be located in close proximity to the alcohol production facility to be efficient and avoid the risk of having to transport EO over long distances. In the case of “P-series” products, a propylene oxide unit also has to be conveniently located. The traditional preparation of PO involves the co-product formation of precursor materials leading to final products such as styrene and MTBE. Other methods to make PO have been developed, as for example, by the use of expensive hydrogen peroxide. The use of PO to make P-series materials thus has cost concerns.
Dioxolane compounds are characterized by having a five-membered ring with oxygen atoms in the 1 and 3 positions. Other materials based on renewable materials can also be used to prepare acetal compounds by known reactions with aldehydes, including glycerin, 1,3-propanediol and sugar-derived polyols such as mannitol, erythritol, 1,2- and 2,3-butanediol, and the like. In some of these other examples a class of acetal compound having a six-membered ring with oxygen atoms in the 1 and 3 positions known as 1,3-dioxanes can be prepared. Ketals may also be prepared by the reaction of ketone hydrocarbons with the above poly hydroxyl hydrocarbons in a similar manner to that of the preparation of acetals.
Previous work has been disclosed in the literature that discusses the hydrogenolysis of acetals, both cyclic and open to produce ether type hydrocarbons. In the case of 1,3-dioxolane acetal compounds, work has been disclosed that describes the preparation of valuable 2-alkoxy ethanol compounds. This chemical transformation is carried out by the cleavage of the oxygen-carbon bond attached to the carbon in the 2-position of the ring with hydrogen using a noble metal catalyst. The focus of that work has been on the liquid-phase hydrogenolysis of acetals in a solvent that is typically the diol moiety used to prepare the cyclic acetal. The art teaches the importance of having a large excess of this diol solvent present during the hydrogenolysis reaction to prevent the formation of significant amounts of undesired co-product, namely a diether.
U.S. Pat. No. 4,479,017 discusses the desire to generate ether compounds in high selectivity and yield by employing a palladium catalyst on a carbon carrier support in the absence of an added acid promoter compound. U.S. Pat. No. 4,484,009 discloses the product of monoethers of monoethylene glycol by hydrogenolysis of an acetal with a co-catalytic system of a palladium catalyst in combination with an acidic phosphorus promoter compound and ethylene glycol. In both instances, the reactions were conducted in the liquid phase. There remains a need to provide suitable catalyst systems that will generate hydroxy ether hydrocarbons in high selectivity in a vapor phase hydrogenolysis process.